Prostate cancer remains the most common non- cutaneous malignancy in the Western world and is the second highest cause of cancer death in men after lung cancer. The main reason for prostate cancer mortality is the failure to cure patients with metastatic disease. A number of publications have demonstrated an increase in expression of vascular endothelial growth factor-C (VEGF-C) in metastatic prostate cancer when compared to primary prostate cancer. Our preliminary results suggest a direct role of VEGF-C in promoting survival of prostate cancer cells during stress. This function of VEGF-C is distinctly different from its known paracrine function of inducing the growth of new lymphatic vessels. We believe that by protecting the prostate cancer cells from stress-induced apoptosis, VEGF-C promotes prostate cancer recurrence and metastasis. Interestingly, in many recent clinical studies, VEGF-C expression is correlated with cancer recurrence, further supporting our findings. We hypothesize that the survival promoting function of VEGF-C during stress is necessary for the development of therapy-resistant and metastatic prostate cancer. The goal of this proposal is to understand the importance of VEGF-C as a prognostic as well as a therapeutic target for refractory, metastatic prostate cancer. Three specific aims will address this goal. In Aim 1, we will elucidate the molecular mechanism of VEGF-C mediated stress resistance of prostate cancer cells. We will determine the involvement of VEGF-C receptor, neuropilin-2 in regulating the mTOR complex-2/AKT-1 pathway in prostate cancer cells under oxidative stress. Our study will therefore provide information about the upstream mechanisms of mTOR complex-2 activation. We will also determine the role of VEGF-C in resisting hypoxic stress in prostate cancer especially after androgen ablation. In aim 2, we will investigate the role of VEGF-C in therapy resistant prostate cancer cells. The stress- resistant function of the VEGF-C/Neuropilin-2/m-TORC-2/AKT-1 axis in prostate cancer cells will be evaluated following ionizing radiation alone or in combination with androgen deprivation. Both in vitro tissue culture models and animal models of prostate cancer (Orthotopic implantation of VEGF-C expressing human prostate cancer cells in immunocompromised mice and transgenic NKX3.1;PTEN knock-out mice) will be used. In aim 3, we will compare the tissue expression levels of VEGF-C and their down-stream targets with the frequency of recurrence of human prostate cancer following prostatectomy. The association of high VEGF-C expression levels with cancer recurrence following prostatectomy will be determined in a cohort of approximately three hundred patients with locally invasive prostate cancer and prostate cancer with metastases in the regional lymph nodes. The role of downstream targets of VEGF-C (e.g. Phospho-AKT-1 (Ser 473), neuropilin-2, phospho c-Met, phospho- FOXO-1 and phospho-mTOR) in promoting survival will also be evaluated. This study should provide potential targets for effective therapeutic interventions as well as prognostic indicators for the metastatic stage of prostate cancer. PUBLIC HEALTH RELEVANCE: This proposal will help to understand the mechanism of metastatic progression of prostate cancer and is therefore important for the development of novel and effective therapies. It will also help to predict the outcome of currently available therapies in prostate cancer patients like radiation and hormonal ablation.